The invention relates to a process for the isolation of alkylated aromatic amines by working up crude catalyst-containing alkylation mixtures of such amines from alkylation with the aid of olefins.
Alkylation of aromatic amines and diamines with olefins in the presence of catalytic amounts of aluminum/aluminum chloride is known (Angew. Chemie 69 (1957), 124-131). This reaction has been extended by the use of aluminum/zinc/aluminum chloride (European Pat. No. 0,150,770). Carrying out this reaction in the presence only of AlCl.sub.3 is furthermore known (European Pat. No. 0,260,251).
After the alkylation reaction, the crude alkylation mixtures are worked up in a known manner by extraction by stirring with excess dilute aqueous sodium hydroxide solution. The contact catalyst dissolved in the organic phase is in this way decomposed and transferred to the aqueous-alkaline layer. The crude alkylated amine can be isolated by separation of the layers and fed to further working up, for example by distillation.
This known working up process has disadvantages, in particular for ecological reasons: because of the industrial importance of this amine alkylation, it is carried out on a large scale, so that large amounts of waste sodium hydroxide solution are obtained as a byproduct. The waste sodium hydroxide solution contains amine impurities which, as a result of poor separation of the layers, are present in emulsified form. It is not possible to dispose of this contaminated waste sodium hydroxide solution without an expensive purification process.